stackoverflow-java-top-qa: stackoverflow上Java相关回答整理翻译

stackoverflow-Java-top-qa
=======================
    对stackoverflow上Java相关、投票数TOP100的问答进行翻译，欢迎点star，我们会持续更新!!!

为了让“翻译”更有意义，给阅读者带来更多、更有效的收获，我们会有一些加工：
    例如，对问题进行分类，整合多个答案、删除冗余内容、加上自己的验证结果、心得等等
    
    对于参与翻译的人，这也是很好的一个学习、理解过程，欢迎大家一起来翻译

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### 如何参与翻译（欢迎加入翻译组QQ群485011036）
如何参与：
- 请从下文“待翻译问题链接”中寻找你感兴趣的问答进行翻译。翻译好的问答，放到contents目录下，无需更新readme.md文档。之后提一个PR，我会对你的翻译做一个审校，并更新到readme中。
- 另外，为了避免多人重复新翻译一个问题，你可以提issue，说明你计划翻译的问题及时间点，我可以先更新到下面的”未翻译问题“中，说明已有人领了这个问题。当然，也不一定要提issue，一般情况下，只要及时提pr，我及时审核，出现”撞车“的概率并不高。

一些基本的约定：
- 文档的文件名，和stackoverflowhich-notnull-java-annotation-should-i-usew上的url保持一致。例如，http://stackoverflow.com/questions/8710619/java-operator 的文件名， 就是java-operator.md
- 在每篇翻译文档内容的最后，要附上stackoverflow的原文链接

每个人可以做（但不限于）：
- 找未翻译的问题进行翻译
- 优化已翻译的问题
- 输出问答精简汇总版（把所有的问答集中到一个md文件，然后尽量精简，让别人可以在一天内把这100个问题的精髓都看完）
- 输出gitbook版本（现在直接在github上查看，体验不好）

### 目录
> 基础语法

* [Java += 操作符实质](https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/java-operator.md)
* [将InputStream转换为String](https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/read-convert-an-inputstream-to-a-string.md)
* [将数组转换为List](https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/create-arraylist-from-array.md)
* [如何遍历map对象](https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/iterate-through-a-hashmap.md)
* [public，protected，private，不加修饰符。有什么区别呢？](https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/in-java-whats-the-difference-between-public-default-protected-and-private.md)
* [如何测试一个数组是否包含指定的值？](https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/how-can-i-test-if-an-array-contains-a-certain-value.md)
* [重写（Override）equlas和hashCode方法时应考虑的问题](https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/what-issues-should-be-considered-when-overriding-equals-and-hashcode-in-java.md)
* [从一个多层嵌套循环中直接跳出](https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/breaking-out-of-nested-loops-in-java.md)
* [如何将String转换为Int](https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/converting-string-to-int-in-java.md)
* [如何分割（split）string字符串](https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/how-to-split-a-string-in-java.md)
* [在java中如何对比（compare）string](https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/how-do-i-compare-strings-in-java.md)
* [`Map<Key,Value>`基于Value值排序](https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/how-to-sort-a-mapkey-value-on-the-values-in-java.md)
* [`HashMap和Hashtable的区别](https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/differences-between-hashmap-and-hashtable.md)
* [如何便捷地将两个数组合到一起](https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/how-to-concatenate-two-arrays-in-java.md)
* [Java 是否支持默认的参数值](https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/does-java-support-default-parameter-values.md)
* [Java 产生指定范围的随机数](https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/generating-random-integers-in-a-range-with-Java.md)
* [JavaBean 到底是什么](https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/what-is-a-javabean-exactly.md)
* [wait()和sleep()的区别](https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/difference-between-wait-and-sleep.md)
* [能否在一个构造器( `constructor` )中调用另一个构造器](https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/how-do-i-call-one-constructor-from-another-in-java.md)
* [ `finally` 代码块总会被执行么](https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/does-finally-always-execute-in-java.md)
* [如何将String转换为enum](https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/convert-a-string-to-an-enum-in-java.md)
* [在Java中声明数组](https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/declare-array-in-java.md)
* [反射是什么及其用途](https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/what-is-reflection-and-why-is-it-useful.md)
* [为什么不能用string类型进行switch判断](https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/why-cant-i-switch-on-a-string.md)
* [比较java枚举成员使用equal还是==](https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/comparing-java-enum-members-or-equals.md)
* [用java怎么创建一个文件并向该文件写文本内容](https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/how-to-create-a-file-and-write-to-a-file-in-java.md)
* [serialVersionUID 有什么作用？该如何使用？](https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/what-is-a-serialversionuid-and-why-should-i-use-it.md)
* [为什么Java的```Vector```类被认为是过时的或者废弃的](https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/why-is-java-vector-class-considered-obsolete-or-deprecated.md)
* [Java的foreach循环是如何工作的](https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/how-does-the-java-for-each-loop-work.md)
* [为什么相减这两个时间（1927年）会得到奇怪的结果](/contents/why-is-subtracting-these-two-times-in-1927-giving-a-strange-result.md)
* [Java 中如何将 String 转换为 enum](/contents/lookup-enum-by-string-value.md)
* [该什么时候使用 ThreadLocal变量，它是如何工作的](/contents/when-and-how-should-i-use-a-threadlocal-variable.md)
* [servlets的运行原理](/contents/how-do-servlets-work-instantiation-shared-variables-and-multithreading.md)
* [如何计算MD5值](/contents/how-can-i-generate-an-md5-hash.md)

> 编程技巧

* [去掉烦人的“!=null"(判空语句](https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/avoiding-null-statements-in-java.md)
* [获取完整的堆栈信息](https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/get-current-stack-trace-in-java.md)
* [如何用一行代码初始化一个ArrayList](https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/initialization-of-an-arraylist-in-one-line.md)
* [初始化静态map](https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/how-can-i-initialize-a-static-map.md)
* [给3个布尔变量，当其中有2个或者2个以上为true才返回true](https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/check-if-at-least-two-out-of-three-booleans-are-true.md)
* [输出 Java 数组最简单的方式](https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/whats-the-simplest-way-to-print-a-java-array.md)
* [为什么以下用随机生成的文字会得出 “hello world”?](https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/why-does-this-code-using-random-strings-print-hello-world.md)
* [什么在java中存放密码更倾向于char[]而不是String](https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/why-is-char-preferred-over-string-for-passwords-in-java.md)
* [如何避免在JSP文件中使用Java代码](https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/how-to-avoid-java-code-in-jsp-files.md)
* [Java 源码里的设计模式](https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/examples-of-gof-design-patterns-in-javas-core-libraries.md)
* [如何产生一个随机的字母数字串作为 session 的唯一标识符](https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/how-to-generate-a-random-alpha-numeric-string.md)
* [如何创建单例](https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/what-is-an-efficient-way-to-implement-a-singleton-in-java.md)
* [实现Runnable接口  VS. 继承Thread类](https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/implements-runnable-vs-extends-thread.md)
* [我应该用哪一个@NotNull注解](https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/which-notnull-java-annotation-should-i-use.md)
* [怎样将堆栈追踪信息转换为字符串](https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/how-can-i-convert-a-stack-trace-to-a-string.md)
* [如何处理 java.lang.outOfMemoryError PermGen space error](https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/dealing-with-java-lang-outofmemoryerror-permgen-space-error.md)
* [如何在整数左填充0](https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/how-can-i-pad-an-integers-with-zeros-on-the-left.md)
* [在调用 instanceof 前需要进行null检查吗](https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/is-null-check-needed-before-calling-instanceof.md)

> 网络

* [如何使用java.net.URLConnection接收及发送HTTP请求](https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/using-java-net-urlconnection-to-fire-and-handle-http-requests.md)

> 性能

* [LinkedList、ArrayList各自的使用场景，如何确认应该用哪一个呢？](https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/when-to-use-linkedlist-over-arraylist.md)
* [StringBuilder和StringBuffer有哪些区别呢](https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/stringbuilder-and-stringbuffer.md)
* [为什么处理排序的数组要比非排序的快](https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/why-is-processing-a-sorted-array-faster-than-an-unsorted-array.md)
* [如何使用Java创建一个内存泄漏的程序](https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/creating-a-memory-leak-with-java.md)
* [为什么打印“B”会明显的比打印“#”慢](https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/why-is-printing-b-dramatically-slower-than-printing.md)

> 测试

* [如何测试 private 方法，变量或者内部类](https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/how-to-test-a-class-that-has-private-methods-fields-or-inner-classes.md)

> Android

* [在Android里面下载文件，并在ProgressDialog显示进度](https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/download-a-file-with-android-and-showing-the-progress-in-a-progressdialog.md)
* [如何获取Android设备唯一ID](https://github.com/giantray/stackoverflow-java-top-qa/blob/master/contents/is-there-a-unique-android-device-id.md)

### 待翻译问题链接(还剩x问题)
- [Proper use cases for Android UserManager.isUserAGoat()?](http://stackoverflow.com/questions/13375357/proper-use-cases-for-android-usermanager-isuseragoat)
- [How can I create an executable jar with dependencies using Maven?](http://stackoverflow.com/questions/574594/how-can-i-create-an-executable-jar-with-dependencies-using-maven)
- [Why is executing Java code in comments with certain Unicode characters allowed?](http://stackoverflow.com/questions/30727515/why-is-executing-java-code-in-comments-with-certain-unicode-characters-allowed)
- [Convert a String to an enum in Java](http://stackoverflow.com/questions/604424/convert-a-string-to-an-enum-in-java)
- [Android SDK installation doesn't find JDK](http://stackoverflow.com/questions/4382178/android-sdk-installation-doesnt-find-jdk)
- [Java inner class and static nested class](http://stackoverflow.com/questions/70324/java-inner-class-and-static-nested-class)
- ['Must Override a Superclass Method' Errors after importing a project into Eclipse](http://stackoverflow.com/questions/1678122/must-override-a-superclass-method-errors-after-importing-a-project-into-eclips)
- [Fastest way to determine if an integer's square root is an integer](http://stackoverflow.com/questions/295579/fastest-way-to-determine-if-an-integers-square-root-is-an-integer)
- [How to fix: Unsupported major.minor version 51.0 error?](http://stackoverflow.com/questions/10382929/how-to-fix-unsupported-major-minor-version-51-0-error)
- [How to generate a random alpha-numeric string?](http://stackoverflow.com/questions/41107/how-to-generate-a-random-alpha-numeric-string)
- [Comparing Java enum members: == or equals()?](http://stackoverflow.com/questions/1750435/comparing-java-enum-members-or-equals)
- [Failed to load the JNI shared Library (JDK)](http://stackoverflow.com/questions/7352493/failed-to-load-the-jni-shared-library-jdk)
- [How to create a Java String from the contents of a file?](http://stackoverflow.com/questions/326390/how-to-create-a-java-string-from-the-contents-of-a-file)
- [How do you assert that a certain exception is thrown in JUnit 4 tests?](http://stackoverflow.com/questions/156503/how-do-you-assert-that-a-certain-exception-is-thrown-in-junit-4-tests)
- [What exactly is Apache Camel?](http://stackoverflow.com/questions/8845186/what-exactly-is-apache-camel)
- [How can I permanently have line numbers in IntelliJ?](http://stackoverflow.com/questions/13751/how-can-i-permanently-have-line-numbers-in-intellij)
- [Access restriction on class due to restriction on required library rt.jar?](http://stackoverflow.com/questions/860187/access-restriction-on-class-due-to-restriction-on-required-library-rt-jar)
- [How do I discover memory usage of my application in Android?](http://stackoverflow.com/questions/2298208/how-do-i-discover-memory-usage-of-my-application-in-android)
- [Uncatchable ChuckNorrisException](http://stackoverflow.com/questions/13883166/uncatchable-chucknorrisexception)
- [Can I add jars to maven 2 build classpath without installing them?](http://stackoverflow.com/questions/364114/can-i-add-jars-to-maven-2-build-classpath-without-installing-them)
- [Update Eclipse with Android development tools v. 23](http://stackoverflow.com/questions/24437564/update-eclipse-with-android-development-tools-v-23)
- [Setting multiple jars in java classpath](http://stackoverflow.com/questions/219585/setting-multiple-jars-in-java-classpath)
- [Iterating through a list, avoiding ConcurrentModificationException when removing in loop](http://stackoverflow.com/questions/223918/iterating-through-a-list-avoiding-concurrentmodificationexception-when-removing)
- [What is the Java equivalent for LINQ?](http://stackoverflow.com/questions/1217228/what-is-the-java-equivalent-for-linq)
- [Hibernate hbm2ddl.auto possible values and what they do?](http://stackoverflow.com/questions/438146/hibernate-hbm2ddl-auto-possible-values-and-what-they-do)
- [How can I pad an integers with zeros on the left?](http://stackoverflow.com/questions/473282/how-can-i-pad-an-integers-with-zeros-on-the-left)
- [Sort ArrayList of custom Objects by property](http://stackoverflow.com/questions/2784514/sort-arraylist-of-custom-objects-by-property)
- [What's the difference between @Component, @Repository & @Service annotations in Spring?](http://stackoverflow.com/questions/6827752/whats-the-difference-between-component-repository-service-annotations-in)
- [Efficiency of Java “Double Brace Initialization”?](http://stackoverflow.com/questions/924285/efficiency-of-java-double-brace-initialization)
- [Why does this go into an infinite loop?](http://stackoverflow.com/questions/3831341/why-does-this-go-into-an-infinite-loop)
- [decompiling DEX into Java sourcecode](http://stackoverflow.com/questions/1249973/decompiling-dex-into-java-sourcecode)
- [How to create a generic array in Java?](http://stackoverflow.com/questions/529085/how-to-create-a-generic-array-in-java)
- [Why does Math.round(0.49999999999999994) return 1](http://stackoverflow.com/questions/9902968/why-does-math-round0-49999999999999994-return-1)
- [Eclipse: Set maximum line length for auto formatting?](http://stackoverflow.com/questions/3697287/eclipse-set-maximum-line-length-for-auto-formatting)
- [What is the difference between a soft reference and a weak reference in Java?](http://stackoverflow.com/questions/299659/what-is-the-difference-between-a-soft-reference-and-a-weak-reference-in-java)
- [What is the equivalent of the C++ Pair<L,R> in Java?](http://stackoverflow.com/questions/156275/what-is-the-equivalent-of-the-c-pairl-r-in-java)
- [What is the difference between JSF, Servlet and JSP?](http://stackoverflow.com/questions/2095397/what-is-the-difference-between-jsf-servlet-and-jsp)
- [How do I “decompile” Java class files?](http://stackoverflow.com/questions/272535/how-do-i-decompile-java-class-files)
- [Useful Eclipse Java Code Templates [closed]](http://stackoverflow.com/questions/1028858/useful-eclipse-java-code-templates)
- [How to call SOAP web service in Android](http://stackoverflow.com/questions/297586/how-to-call-soap-web-service-in-android)

### contributors

thx a lot:)

- [giantray](https://github.com/giantray)

- [wklken](https://github.com/wklken)

more [link](https://github.com/giantray/stackoverflow-java-top-qa/graphs/contributors)

------

To Be Continue ...

giantray

Email: lizeyang@foxmail.com

Blog: http://blog.csdn.net/lizeyang

2015-08-18 于珠海

冷色探戈/stackoverflow-java-top-qa

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